/*
 * @lc app=leetcode.cn id=341 lang=cpp
 *
 * [341] 扁平化嵌套列表迭代器
 */
/**
 * // This is the interface that allows for creating nested lists.
 * // You should not implement it, or speculate about its implementation
 * class NestedInteger {
 *   public:
 *     // Return true if this NestedInteger holds a single integer, rather than a nested list.
 *     bool isInteger() const;
 *
 *     // Return the single integer that this NestedInteger holds, if it holds a single integer
 *     // The result is undefined if this NestedInteger holds a nested list
 *     int getInteger() const;
 *
 *     // Return the nested list that this NestedInteger holds, if it holds a nested list
 *     // The result is undefined if this NestedInteger holds a single integer
 *     const vector<NestedInteger> &getList() const;
 * };
 */
class NestedIterator
{
public:
    NestedIterator(vector<NestedInteger> &nestedList)
    {
        for (int i = nestedList.size() - 1; i >= 0; --i)
        {
            s.push(nestedList[i]);
        }
    }

    int next()
    {
        NestedInteger t = s.top();
        s.pop();
        return t.getInteger();
    }

    bool hasNext()
    {
        while (!s.empty())
        {
            NestedInteger t = s.top();
            if (t.isInteger())
                return true;
            s.pop();
            for (int i = t.getList().size() - 1; i >= 0; --i)
            {
                s.push(t.getList()[i]);
            }
        }
        return false;
    }

private:
    stack<NestedInteger> s;
};

/**
 * Your NestedIterator object will be instantiated and called as such:
 * NestedIterator i(nestedList);
 * while (i.hasNext()) cout << i.next();
 */
